Technical Field
This invention concerns a method for monitoring a cable strand containing multiple electrical lines, specifically electrical energy lines. Furthermore, this invention concerns a monitoring device for monitoring a cable strand containing multiple electrical lines, and this invention concerns a wind turbine.
Description of the Related Art
It is known that electrical energy from an electrical generator in a wind turbine can be transferred through electrical lines in a wind turbine tower down to the tower base, so that this electrical energy can be transferred on from there and/or processed further. In one well-known example, the generator generates alternating current, for example in the form of two three-phase alternating currents. These alternating currents are rectified in the nacelle, where the generator is located, and the direct current generated in this process is conducted from the nacelle via direct current lines, and therefore from the top of the tower downwards to the tower base. To achieve this, multiple identical lines are normally arranged in parallel to avoid the line being too thick and therefore difficult to handle, and the total line cross-section required is achieved by using multiple parallel-connected lines. For example, these lines may be electrically connected in the top of the tower and base of the tower via a terminal busbar. For example, this would allow 16 lines to be connected in parallel, such that they are electrically, and therefore galvanically, connected to one another at this busbar. The direct current generated is then supplied to this busbar or a similar component, and ideally will be uniformly distributed along the individual lines. The uniform distribution of the current on the electrical lines is basically limited physically. If all the lines are specifically of the same cross-section and the same length, i.e., about the length of the tower, they will have the same ohmic resistance, i.e., in general they will have the same impedance. Accordingly, each line carries the same current.
In reality, it may be that there are defects or at least unacceptable inaccuracies. This means, for example, that occasional high transfer resistances, interruptions, short-circuits or the like may occur, which may cause an excessively high current in one of the lines. Faulty or poorly connected individual lines can mean that less—or in the worst case, absolutely no—current flows, and the other lines must correspondingly take on and carry more current.
The German Patent and Trademark Office has researched the following prior art in the priority application for this application: DE 10 2009 021 217 A1 und EP 2 270 452 A2.